20 mule teams were used because of the great strength of the mules and the large loads that were being hauled. Something a little different about the way these teams were hitched was that rather than the wooden draw poles and eveners we're used to seeing with smaller teams, the mules would be hitched in pairs to a long chain. The mules had to be taught to "jump the chain" for the purpose of rounding corners. While the lead teams, some distance from the load being hauled, would begin to round a corner, the mules closer to the load and on the inside of the curve had to jump to the outside of the chain so that even and straight draw was maintained until the load reached the corner.
Another difference was that the driver did not ride the load but rather rode one of the horses at the lead of the team or often worked on foot as the pace was not great. He would be assisted by a team of outriders or walkers placed at intervals along the team to help direct the movements. There were persons who rode the load or wagons and their purpose was as brakemen. One of the interesting comments in the article is that the locomotive had to be drawn downhill. This is where the brakemen played a vital role as the weight of the load would've quickly overtaken the team and run it over.
People often wonder why farmers bothered to breed mules, an animal that can't reproduce. Mules inherit the strength of the horse but also the guile and intelligence of the donkey. The combination makes for an animal that is exceedingly strong and suited its purpose and, perhaps, less prone to the flights of will that might be caused by hormones.